Urban Forestry and Climate Change - UNECE · Cities and climate change • Cities are major...
Transcript of Urban Forestry and Climate Change - UNECE · Cities and climate change • Cities are major...
Urban Forestry and Urban Forestry and Climate ChangeClimate Change
Prof. Dr. Cecil C. KonijnendijkDanish Centre for Forest, Landscape and Planning
University of Copenhagen
OutlineOutline
• Urbanisation and introducing urban forestry• Urban forests are impacted by climate change• Urban forestry and mitigation• Urban forestry and adaptation• Urban forestry and climate change: the wider agenda• What cities can do
Cities and climate changeCities and climate change
• Cities are major emitters of greenhouse gases• Cities are highly vulnerable to impacts of
climate change– Droughts, heat waves, flooding, pollution, ...
• Cities have become active in mitigation, but less so in terms of adaptation
• Time to put in place adaptive measures, e.g. In terms of rethinking urban design and management
• Important role for green space
““Playing FieldPlaying Field”” of Urban Forestryof Urban Forestry
The Urban Forest
Individual trees
Tree groups and small woods (e.g.
in parks)
Urban & peri-
urban woodlands
Functions, policies,
planning, and design
Technical
activities, including selection and establishment
Management
Modified from Konijnendijk & Randrup (2002) Urb. For. & Urb. Green. 1:1-4.
Credits: Thomas Randrup
Urban forests: affected by climate changeUrban forests: affected by climate change
• Changes in temperatures, drought, wind, etc.• Impacts on growing conditions, species choice• Extreme weather conditions, hurricanes, flooding• Expected increases in (invasive) pests and diseases• Urban-wildland interface: more frequent fires
Wikimedia Commons
Urban forests and Urban forests and climate change mitigation (1)climate change mitigation (1)
• Do urban forests sequester carbon?• YES, see various studies:
– United States: 93 kg C/yr for large, healthy trees – 1 kg C/yr for small trees (Nowak 1994, 2006)
– Beijing urban forest: 0.2 million tons of C stored by 2.4 million trees (Yang et al. 2004)
• BUT, direct contributions are still relatively small:– Considering present emission trading etc.: only few, specially
designed urban tree projects are cost effective (McHale et al. 2007)
– Sequestration by urban forests minor in comparison to GHG emissions from urban areas
Urban forests and Urban forests and climate change mitigation (2)climate change mitigation (2)
• Some of the problems with urban trees and carbon sequestration:– Low survival rates of urban trees; many stresses– Not many large trees (short life span)– Dead/removed trees: within 1 year, up to 80% of
carbon is released (McPherson & Simpson 2000)
– High costs of urban tree planting and management (while carbon credits still have a low value)
• ... But also some opportunities– E.g. tree planting and greening campaigns,
afforestation policies
Urban forestry and Urban forestry and climate change adaptation(1)climate change adaptation(1)
• Lower temperatures (‘urban heat island’) through shading, evapo-transpiration
• Reduce flooding• Reduce air pollution• Buffering of extreme
winds
Urban forestry and Urban forestry and climate change adaptation (2)climate change adaptation (2)
• Moderation of urban micro-climates (e.g. Eliasson et al., 2007; Shashua-Bar et al., 2009)
– Shading, evapo-transpiration, etc.– Comfort and recreational use– Trees as cost-effective cooling
mechanism
• Reducing energy needs for cooling and heating (e.g. Nowak 1993, McPherson 1998)
– Trees close to buildings: shading, reducing wind
– Cooling effects and air conditioning
ASCCUE ASCCUE Adaptation to climate change in the urban environmentAdaptation to climate change in the urban environment
19611961--1990 Surface Temperatures 1990 Surface Temperatures (Greater Manchester)(Greater Manchester)
15:4
2
15:3
0
15:0
0
15:0
0
15:1
2
14:4
8
13:1
2
15:0
0
13:1
8
14:3
6
14:3
6
14:1
8
14:3
0
13:1
2
13:5
4
13:4
8
13:1
8
13:1
8
13:0
6
13:1
8
13:1
8
13:1
8
13:1
2
13:1
2
13:1
2
13:0
6
13:0
6
13:0
6Time of max temp
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eatm
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UMT
Max
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)
0.00.10.20.30.40.50.60.70.80.91.0
Evap
otra
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prop
ortio
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max surface temp evaporating fraction
Urban forestry and climate change: Urban forestry and climate change: the wider agendathe wider agenda
• Urban forests have important educational functions– Raising public awareness– Learning how to deal with climate change
• Urban forests have important symbolic functions– Mitigation at people’s doorstep, where most
emissions occur– Facilitating local action, acting as a ‘flagship’– Action in the centre of power and the
political debate
What cities can doWhat cities can do
• Include urban forestry in climate mitigation and adaptation strategies:– Part of climate change strategies– Rethinking urban design and management
• Make climate agenda a part of green space management
• Use urban forests as test and demonstration areas
• Apply urban forestry for awareness raising about climate change mitigation and adaptation